Get the decals from Keystone even if you have to pay for them. Much cheaper than having them made custom.
If you want to save some money, remove the decals yourself using a heat gun. Its not hard, just boring and tedious work.
Find a vehicle wrap company to do the install work. They do it daily and the finished product will be much better. Baring that, starting calling window tent companies...
Another route is to have the whole trailer wrapped in a custom design. It will be a few grand but the look will be one of a kind. The wrap can be removed down the road and the exterior will be good as new...